subliminal priming

[Peter Quain]

to get 6-7ms duration your monitor must be running at ~ 142Hz - 
that's a fast refresh! You must be using canvas (I assume, because 
you are using WritePort commands). Anyway, say your monitor is set to 
100Hz. You should be able to copy from offscreen canvas at the start 
of a refresh, and follow the copy command with a writeport then Sleep 
for 7ms, then zero the port, and fit it all in the 10ms refresh. I 
thought Neuroscan equipment liked pulsewidths of a few ms, and my old 
lab had no worries with 7ms duration pulses.

  At 11:38 PM 22/08/2009, you wrote:

>Hi Ben,
>
>tried to add 'Sleep x' in between the two 'WritePort' but
>unfortunately it did not do the trick.
>
>It actually did with 'Sleep 40', but considering my stimuli (type 1)
>last about 6-7ms that delay is obviously infeasible.
>I can still use the data (getting the event table, correcting it with
>a custom script in matlab and then epoching in Neuroscan according to
>the modified event table file) even though, as you may understand, it
>is kind of a pain..
>
>In fact, given that there must be a way to get the triggers sent right
>and neat in the first place, it feels quite annoying to have to
>correct them after each session.
>
>Once again, any help on how to send triggers for short-lasting stimuli
>(we are experiencing problems for any length<100ms) would be much
>appreciated.
>
>Thank you,
>vinz.
>
>On Aug 18, 6:31 pm, vinz <godotworkaro... at googlemail.com> wrote:
> > Thank you Ben,
> > I will try it out tomorrow, and then let you know.
> >
> > Thank you again.
> > vinz.
> >
> > On Aug 18, 3:25 pm, ben robinson <baltimore.... at gmail.com> wrote:
> >
> > > maybe you you'd want to sleep for 10 ms before sending the 
> "WritePort &H378,
> > > 0"... just a suggestion, won't necessarily fix it.
> > > ben
> >
> > > On Tue, Aug 18, 2009 at 9:42 AM, vinz 
> <godotworkaro... at googlemail.com>wrote:
> >
> > > > Hello group,
> >
> > > > I am current running a subliminal ERP study. Everything is fine as far
> > > > as the implementation of subliminal stimuli is concerned but we are
> > > > experiencing problems with the triggers from E-Prime to the Neuroscan
> > > > station.
> >
> > > > Specifically, we have noticed that any time E-Prime sends a trigger
> > > > relative to a slide presented for a time between 100ms and 20ms (we
> > > > don't have anything in between this two values, so I cannot be more
> > > > specific) the trigger is sent twice, also affecting the following
> > > > slide (presented for about 500ms).
> >
> > > > For the sake of clearness, the event table in Neuroscan looks like
> > > > this:
> >
> > > > 1 3 3 7 7 1 |1| 3 |3| 3 7 7 3 3 1
> >
> > > > instead of:
> >
> > > > 1 3 3 7 7 1 3 3 7 7 1 3 3 7 7 1
> >
> > > > where '1' is the trigger code for the subliminal stimulus, and |1|,|3|
> > > > are actually doubled. In fact the latencies for the first 1 and the
> > > > second |1| are equal. The same happens for 3 and |3|.
> >
> > > > Being most likely a problem caused by incorrect trigger settings in
> > > > the InLine procedures, here it is what we are using:
> >
> > > > WritePort &H378,1
> > > > WritePort &H378,0
> >
> > > > WritePort &H378,3
> > > > WritePort &H378,0
> >
> > > > WritePort &H378,7
> > > > WritePort &H378,0
> >
> > > > If anyone is familiar with E-Prime triggers and has a suggestion to
> > > > give, I would greatly appreciate.
> >
> > > > Thank you,
> > > > vinz.
> >
> > > > On Aug 17, 9:19 am, liwenna <liwe... at gmail.com> wrote:
> > > > > Hey,
> >
> > > > > I looked around a bit and I think the link in this page downloads a
> > > > > estudio file with subliminal exposure in it:
> > > >http://www.docstoc.com/docs/5417962/Instructions-for-running-th 
> e-E-Pr....
> > > > > It's part of some book... and it also mentions some other usefull
> > > > > things. I think there really isn't all that much special to 
> the design
> > > > > of a subliminal task... simply make the exposureduration on the
> > > > > primeslide really short (dependent on the exact nature of your task)
> > > > > and ussually you'll want to show a mask right after your prime but
> > > > > this is, again, dependent on the nature of your task. Then consider
> > > > > options like enabling preloading and disabling showafter (all should
> > > > > be explained in the mentioned chapter in the user-guide), and make
> > > > > sure that your hardware is actually capable of subliminal
> > > > > presentation.
> >
> > > > > Greetz,
> >
> > > > > liwenna
> >
> > > > > On Aug 17, 8:25 am, Kim Janssens <kim.jansse... at gmail.com> wrote:
> >
> > > > > > Hello liwenna,
> >
> > > > > > Thank you for your fast reply: the advice on the refresh 
> rate is really
> > > > > > helpful! If I come across any specific problems when 
> building, I will
> > > > post
> > > > > > my question again.
> >
> > > > > > greetz,
> > > > > > Kim
> > > > > > ps: do you know where i could find an example of 
> experiments designed
> > > > for
> > > > > > subliminal priming? they could help me on the way..
> >
> > > > > > 2009/8/15 liwenna <liwe... at gmail.com>
> >
> > > > > > > Hello Kim,
> >
> > > > > > > Perhaps you could elaborate a bit on what part of designing the
> > > > > > > experiment you need help with.
> > > > > > > In general I think you should start with reading chapter 3 and
> > > > > > > appendix A of the user guide (top of my head), which 
> deal with timing
> > > > > > > issues, obviously important for subliminal priming. 
> Only other thing
> > > > > > > that I can think of now is the monitor issue... make 
> sure that you
> > > > use
> > > > > > > a monitor (when doing the experiment) that is actually capable of
> > > > > > > subliminal-range exposure time i.e. has a sufficiently 
> high enough
> > > > > > > refresh rate.
> >
> > > > > > > I'm guessing that you're relatively new to e-prime 
> (forgive me if I'm
> > > > > > > wrong there). I think it's the most easiest if you simply start
> > > > > > > building and post back here with problems that you 
> encounter along
> > > > the
> > > > > > > way.
> >
> > > > > > > Good luck with it!
> >
> > > > > > > liwenna
> >
> > > > > > > On Aug 14, 2:20 pm, kimio <kim.jansse... at gmail.com> wrote:
> > > > > > > > Hello group,
> >
> > > > > > > > I want to design an experiment in eprime in which I 
> want to show
> > > > the
> > > > > > > > participants a set of pictures and subliminally prime 
> them with a
> > > > word
> > > > > > > > in between the pictures.. Does anyone have any experience with
> > > > this?
> > > > > > > > All help is welcome...
> >
> > > > > > > > thanks,
> > > > > > > > Kim
>

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